Atherosclerosis xxx (2011) xxx xxx Contents lists available at ScienceDirect Atherosclerosis journal homepage: www.elsevier.com/locate/atherosclerosis TNFA 308 (rs1800629) polymorphism is associated with a higher risk of cardiovascular disease in patients with rheumatoid arthritis Luis Rodríguez-Rodríguez a,b,1, Carlos González-Juanatey c,1, Rogelio Palomino-Morales a, Tomás R. Vázquez-Rodríguez d, José A. Miranda-Filloy d, Benjamin Fernández-Gutiérrez b, Javier Llorca e, Javier Martin a,2, Miguel A. González-Gay f,,2 a Instituto de Parasitología y Biomedicina López-Neyra, C.S.I.C., Parque Tecnológico de Ciencias de la Salud, Avenida del Conocimiento s/n Armilla, Granada 18100, Spain b Department of Rheumatology, Hospital Clinico San Carlos, c/ Profesor Martín Lagos, s/n, Madrid 28040, Spain c Cardiology Division, Hospital Xeral-Calde, c/ Dr.Ochoa s/n, Lugo 27004, Spain d Department of Rheumatology, Hospital Xeral-Calde, c/ Dr. Ochoa s/n, Lugo 27004, Spain e Department of Epidemiology and Computational Biology, School of Medicine, University of Cantabria, and CIBER Epidemiología y Salud Pública (CIBERESP), IFIMAV, Avda. Herrera Oria s/n, 39011 Santander, Spain f Department of Rheumatology, Hospital Universitario Marqués de Valdecilla, IFIMAV, Avenida de Valdecilla s/n, 39008 Santander, Spain article info abstract Article history: Received 5 August 2010 Received in revised form 2 October 2010 Accepted 5 October 2010 Available online xxx Keywords: Rheumatoid arthritis Atherosclerosis Cardiovascular disease Genetics TNFA rs1800629 Objective: To assess the influence of the TNFA rs1800629 (G > A) polymorphism in the risk of cardiovascular (CV) disease and subclinical atherosclerosis in patients with rheumatoid arthritis (RA). Methods: 587 patients fulfilling the 1987 American College of Rheumatology classification criteria for RA were studied. Patients were genotyped for the TNFA rs1800629 polymorphism using predesigned TaqMan single nucleotide polymorphism genotyping assay. Also, HLA-DRB1 genotyping was performed using molecular based methods. Carotid artery intima-media thickness, flow-mediated endotheliumdependent and endothelium independent vasodilatation, used as surrogate markers of subclinical atherosclerosis, were measured in a subgroup of patients. Results: We observed a higher frequency of carriers of the minor allele A among the patients with CV disease (with 37.6% vs. without 27.9%, p = 0.06, OR 1.56 [95% confidence interval-ci 0.95 2.54]). Carriers of the minor allele A exhibited a higher risk of CV events after adjustment for demographic and traditional CV risk factors (p = 0.023, HR 1.72 [95% CI 1.076 2.74]). Also, a significant interaction between this polymorphism and the presence of the rheumatoid shared epitope (SE) was observed (p = 0.024). Due to this, the association between carriers of the minor allele A and CV disease was only present in carriers of the SE, even after adjustment (p = 0.001, HR 2.43 [95% CI 1.41 4.19]). No significant association between the TNFA variant and the surrogate markers of subclinical atherosclerosis was observed. Conclusion: Our results show that TNFA rs1800629 gene polymorphism is associated with predisposition to CV complications in patients with RA. This predisposition is restricted to individuals carrying the rheumatoid SE. 2011 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Abbreviations: HLA, human leukocyte antigen; TNF, tumor necrosis factor; RA, rheumatoid arthritis; CV, cardiovascular; OR, odds ratio; CI, confidence interval; FMD, endothelium-dependent-flow-mediated vasodilatation-(post-ischemia); NTG, endothelium independent- (post-nitroglycerin) vasodilatation; RF, rheumatoid factor; Anti-CCP, anti-cyclic citrullinated peptide antibodies; IMT, intima-media thickness; ANOVA, analysis of variance; ANCOVA, analysis of covariance. Corresponding author. Tel.: +34 942 20 25 10; fax: +34 942 20 16 95. E-mail address: miguelaggay@hotmail.com (M.A. González-Gay). 1 These authors had equal contribution. 2 These authors shared authorship in this study. Rheumatoid arthritis (RA) is a chronic inflammatory disease associated with high risk of cardiovascular (CV) events due to accelerated atherosclerosis [1,2]. In this regard, CV disease is the most common cause of mortality in patients with RA [3]. Both traditional (classic) [4] and non-traditional CV risk factors such as chronic inflammation [5] have been implicated in the elevated CV morbidity observed in these patients. Since the outcome of patients with RA is strongly linked to the development of accelerated atherosclerosis and CV complications [1 3] and RA is a complex polygenic disease, an issue of major importance is to determine the genetic implication in the risk of 0021-9150/$ see front matter 2011 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.atherosclerosis.2010.10.052
2 L. Rodríguez-Rodríguez et al. / Atherosclerosis xxx (2011) xxx xxx CV morbidity of these patients. With respect to this, we previously observed a contribution of the human leukocyte antigen (HLA)- DRB1 gene to the risk of endothelial dysfunction, CV events and CV mortality in Spanish individuals with RA [5,6]. Also, we reported a contribution of the inducible and endothelial nitric oxide synthase (NOS2A and NOS3) gene polymorphisms to CV event risk in patients with RA [7]. Moreover, we have recently reported an implication of the methylene tetrahydrofolate reductase (MTHFR) A1298C gene polymorphism in the increased risk of atherosclerosis of patients with RA [8]. Tumor necrosis factor-alpha (TNF- ) is a potent immunomediator and proinflammatory cytokine that has been implicated in the pathogenesis of a large number of human diseases, including RA [9] and atherosclerosis [10]. TNF- mediates a wide variety of effector functions that are of major importance in the pathogenesis of RA, including endothelial cell activation and chemokine amplification leading to leukocyte accumulation, osteoclast and chondrocyte activation promoting joint destruction, nociceptor sensitization and development of metabolic syndrome [9]. In atherosclerosis, TNF- activates inflammatory and endothelial cells, induce a prothrombotic state as well as insulin resistance and dyslipidemia [10]. TNF- synthesis is tightly regulated at the level of gene transcription, and its production may have a genetic component of approximately 60% [11]. A single nucleotide polymorphism located at position 308 in the TNFA promoter (G > A, rs1800629) has been associated with enhanced spontaneous or stimulated TNF- production both in vitro and in vivo [12,13]. However, circulating TNF- level does not seem to be influenced by this polymorphism. While TNFA rs1800629 polymorphism has been considered to be a risk factor in some autoimmune diseases such as insulin-dependent diabetes mellitus and systemic lupus erythematosus [12], the potential association of this polymorphism with RA has shown contradictory results. In this regard, a recent meta-analysis disclosed that this polymorphism may be a risk factor for RA in Latin Americans but not in Europeans [14]. Moreover, TNFA polymorphism has not been confirmed to be a predictor of the clinical response to anti-tnf treatment in RA [15,16]. Since the incidence of coronary artery disease is a function of the development and progression of atherosclerosis, the use of noninvasive surrogate markers of atherosclerosis may be useful for the diagnosis of CV disease through the identification of subclinical disease. Noninvasive imaging techniques provide an approach for identifying high-risk individuals who may benefit from active intervention to prevent clinical disease. They offer a unique opportunity to study the relation of surrogate markers to the development of atherosclerosis. Among them, ultrasound techniques based on flow velocity and intima thickness are considered an efficient way to measure the subclinical atherosclerosis. There are some other noninvasive imaging modalities such as coronary, and aorta imaging, left ventricular echocardiography imaging, electron-beam computed tomography, magnetic resonance imaging, and ankle brachial index. Taking into account all these considerations and the central role played by TNF- in RA and atherosclerosis, in the present study we aimed to determine the influence of TNFA rs1800629 polymorphism in the increased incidence of CV events observed in patients with RA. Considering the previously reported high experience of our group in the assessment of subclinical atherosclerosis in different rheumatic diseases using ultrasound techniques, in the present study we also assessed whether the TNFA rs1800629 (G > A) gene polymorphism might be associated with an increased risk of subclinical atherosclerosis manifested by the presence of endothelial dysfunction or increased carotid artery intima-media wall thickness (IMT). 2. Patients and methods 2.1. Patients and study protocol Between March 1996 and March 2008, 608 consecutive patients that fulfilled the 1987 American College of Rheumatology classification criteria for RA [17] were recruited from the rheumatology outpatient clinics of Hospital Xeral-Calde, Lugo and Hospital Clínico San Carlos, Madrid, Spain. A DNA sample (see below) was extracted from these patients at the time of recruitment. Between December 2009 and January 2010 patient s clinical records were examined until patient s death, loss of follow-up or December 1st, 2009. Sociodemographical and clinical data regarding clinical manifestations, classic CV risk factors and history of CV events were registered. Clinical definitions for CV events and classic CV risk factors were established as previously described [5,18]. In this regard, patients were considered to have diabetes mellitus if before disease diagnosis they had been diagnosed as having diabetes mellitus by their family physicians or if 2 fasting plasma glucose levels on different days at the time of disease diagnosis or over the extended follow-up were >125 mg/dl [5]. Smoking habit was considered to be present in those patients who smoked at the time of disease diagnosis, during the follow-up or who had smoked within the 10 years before the onset of RA symptoms or the disease diagnosis. A CV event was considered to be present if the patient had ischemic heart disease, heart failure, cerebrovascular accident or peripheral arteriopathy. The definition of ischemic heart disease (IHD) included acute coronary syndromes with or without persistent ST-segment elevation and chronic coronary heart disease. IHD was diagnosed if any of the following criteria were satisfied: a recorded diagnosis of ischemic cardiopathy, on account of some acute coronary syndrome (acute myocardial infarction or unstable angina), the presence of pathological Q waves in the electrocardiogram, and coronary images showing >50% stenosis of at least one coronary vessel [5]. Data regarding the clinical presentation of heart failure were also collected from all patients, based on the Framingham criteria [18]. A patient was considered to have a cerebrovascular accident when he/she had a stroke and/or transient ischemic attacks (TIAs). Strokes were classified according to their clinical features and they were confirmed by computed tomography and/or magnetic resonance imaging. TIAs were diagnosed if the symptoms were self-limited in less than 24 h, without residual neurological damage [5]. Peripheral arterial disease was considered to be present if it was confirmed by Doppler and arteriography [19]. Information on the main demographic characteristics, CV risk factors and CV events of patients in whom genotyping success was achieved (n = 587 [97%]) is shown in Table 1. Genotype and allele distribution in our RA sample was similar to that previously described in non-ra healthy Spanish population [20]. Since Hospital Xeral-Calde and Hospital Clínico San Carlos are the referral centers for the population of each respective area, the first CV event was defined as an event (case) of CV complication diagnosed at the hospital in a patient without a previous history of CV disease. Based on previously established protocols of management, all patients on methotrexate therapy were treated with folate supplementation. To determine the potential association between the TNFA rs1800629 polymorphism and the presence of subclinical atherosclerosis, between March 2007 and September 2009 a random subgroup of patients from the Lugo cohort with no previous history of CV events was selected. Presence of endothelial dysfunction was assessed by a brachial artery reactivity study in 130 patients. Flow-mediated endothelium-dependent vasodilatation- FMD (post-ischemia) and endothelium-independent-ntg (postnitroglycerin) vasodilatation were measured by brachial ultra-
L. Rodríguez-Rodríguez et al. / Atherosclerosis xxx (2011) xxx xxx 3 Table 1 Demographic characteristics and genotype distribution of the patients with rheumatoid arthritis included in the study. Variables n = 587 Females 435 (74.1) Age of patients at the time of disease 56 [45 65] diagnosis, years, median [IQR] Time follow-up, years, median [IQR] 13.5 [7 18] Anti-CCP positive (n = 401) 243 (60.6) Rheumatoid factor positive (n = 581) 435 (74.9) Shared epitope (n = 526) 344 (65.4) HLA-DR3 (n = 479) 57 (11.9) Cardiovascular events 93 (15.8) Ischemic heart disease 51 (8.7) Cerebrovascular accidents 27 (4.6) Heart failure 23 (3.9) Peripheral arteriopathy 7 (1.2) Hypertension (n = 583) 219 (37.6) Diabetes mellitus (n = 583) 67 (11.5) Dyslipidemia (n = 583) 244 (41.9) Obesity (n = 583) 59 (10.1) Smoking habit (n = 581) 103 (17.7) TNFA rs1800629 GG 414 (70.5) GA 156 (26.6) AA 17 (2.9) G 984 (83.8) A 190 (16.2) Except where indicated otherwise, values are n (%). IQR, interquartile range; anti- CCP, anti-cyclic citrullinated peptide antibodies. sonography as previously reported [6,21]. A value of FMD less than 7% was considered pathologic, indicating the presence of endothelial dysfunction [21]. Intra-observer variability for FMD and NTG was 1.3% and 1.9%, respectively, based on the repeat of the brachial ultrasonography in 32 healthy controls. Assessment of endothelial function of patients undergoing anti-tnf therapy was performed 24 48 h before drug administration. Also, carotid ultrasonography studies were performed in 108 patients to determine the carotid artery IMT. It was assessed in the right common carotid artery as previously reported [22]. Based on a second carotid ultrasonography performed to 20 RA patients and 20 healthy controls within a week after the first assessment, the correlation coefficient for carotid IMT was 0.98. The subject s written consent was obtained according to the declaration of Helsinki, and the design of the work was approved by the Ethics Committee of Galicia (Spain). The Ethics Committee of the Hospital Clinico San Carlos (Madrid) also approved the study. 2.2. Genotyping 2.2.1. TNFA genotyping DNA from patients was obtained from whole peripheral blood, using standard methods. Subjects were genotyped to determine TNFA rs1800629 status using TaqMan Assays-on-Demand from Applied Biosystems following the manufacturer s protocol and analyzed using the ABI 7900HT Fast Real-Time PCR System (Applied Biosystems, Foster City, CA, USA). The typing was successful in 587 patients (96.5%). Also, 10% of the samples were re-genotyped at random. However, no differences were observed with the results obtained before. 2.2.2. Shared epitope and DR3 determination Several HLA-DRB1 alleles (HLA-DRB1*0401, *0404, *0405, *0408, *0101, *0102, *1001, and *1402) are associated with susceptibility to RA. These alleles encode a conserved amino acid sequence (QKRAA, QRRAA, or RRRAA), called the shared epitope (SE), at position 70 74 in the third hypervariable region of the HLA-DR 1 molecule [23]. HLA-DRB1 typing was carried out using a reverse dot-blot kit with sequence-specific oligonucleotide (SSO) probes (Dynal RELITM SSO HLA-DRB1 typing kit; Dynal Biotech, Bromborough, UK). When necessary, high-resolution typing of HLA-DRB1*03 samples was performed using Dynal AllSetTM SSP DRB1*03. In our RA sample, 65.4% of the patients had at least one copy of the rheumatoid SE, which was a frequency higher than that described in non-ra Spanish individuals [24]. 2.3. Statistical analysis Comparison of means was performed using T-test. Comparison of proportion between 2 or more group was carried out using 2 test or Fisher test, when required. Hardy Weinberg (HWE) equilibrium was tested in the RA patients with and without CV disease. Both groups were in HWE (RA with CV disease p = 0.99, RA without CV disease p = 0.60). Strength of association between CV events and genotypes of the TNFA rs1800629 polymorphism was estimated using odds ratios (ORs) and 95% confidence intervals (CIs), via multiple logistic regression; estimates were further adjusted for gender, age at RA diagnosis, time of follow-up, presence or absence of SE and classic (traditional) CV risk factors (hypertension, diabetes mellitus, dyslipidemia, obesity and smoking habit) as potential confounders. The study had an 80% power for detecting an OR 2. Later, a statistical interaction between TNFA rs1800629 polymorphism and presence or absence of SE was introduced in the logistic regression model. A Cox regression model was used to estimate the influence of the TNFA rs1800629 polymorphism on CV disease. We used the occurrence of at least one CV event as the outcome and the survival time when the first CV event occurred. The survival time of individuals without CV events was the age at patient s death, loss of follow-up or December 1st, 2009. Patients who died of any other causes different from CV events were considered as not having CV events. Proportional hazard assumption was tested using Schoenfeld residuals. Results were expressed as hazard ratios (HRs) with 95% confidence intervals [95% CIs] and were computed as both crude and adjusted for age at RA diagnosis, gender and classic CV risk factors. The selected variables used for adjustment were selected due to their association with the outcome (CV event) and the exposure (rs1800629 genotype) and because they produced a change greater than 10% in the HR. The association between genotypes of the TNFA rs1800629 gene polymorphism and carotid IMT, FMD%-endothelium dependent vasodilatation and NTG%-endothelium independent vasodilatation was also tested using analysis of covariance (ANCOVA) adjusting for gender, age and duration of the disease at the time of the ultrasonographic study, and presence or absence of the SE and traditional CV risk factors. This study had 80% power to detect a difference in carotid intima-media thickness of 0.1 mm or higher, a difference of 2.5% or higher in FMD-endothelium-dependent vasodilatation and a difference of 3.5% or higher in NTG-endothelium-independent vasodilatation. Statistical significance was defined as p 0.05. Calculations were performed with STATA 10 (STATA Corporation, College Station, Texas). 3. Experimental results 3.1. Influence of TNFA rs1800629 polymorphism in the risk of CV events We compared the genotypic and allelic frequencies of the TNFA rs1800629 polymorphism between the subgroup of RA patients that suffered CV events and those who did not experience such CV complications (Table 2). We found an increased frequency of homozygous and heterozygous for the minor allele A (GA + AA
4 L. Rodríguez-Rodríguez et al. / Atherosclerosis xxx (2011) xxx xxx Table 2 Differences between RA patients with CV events or without CV events according to TNFA rs1800629 polymorphism. TNFA rs1800629 genotype n (%) With CV events Without CV events p OR [95% CI] GG 58 (62.4) 356 (72.1) 1 GA 31 (33.3) 125 (25.3) 0.087 1.52 [0.94 2.46] AA 4 (4.3) 13 (2.6) 0.280 1.89 [0.60 5.99] GA + AA 35 (37.6) 138 (27.9) 0.060 1.56 [0.95 2.54] Allele 2n (%) G 147 (79.0) 837 (84.7) 1 A 39 (21.0) 151 (15.3) 0.053 1.47 [0.97 2.22] CV, cardiovascular; OR [95% CI], odds ratio with 95% confidence interval. genotypes) among patients who experienced CV events (37.6% vs. 27.9% in those without CV events, p = 0.06, OR 1.56 [95% CI 0.95 2.54]). Also, the minor allele A frequency was increased among the RA patients with CV events (21.0% vs. 15.3%, p = 0.053, OR 1.47 [95% CI 0.97 2.22]). Taking into account these results, we performed a Cox regression model to account for the variation of risk of the first CV event through time according to the TNFA rs1800629 polymorphism, assuming a dominant model of effect (carriers of the minor allele A vs. non carriers: GA + AA vs. GG). In the crude analysis we observed a non significant increased high risk for the carriers of the minor allele A over time (p = 0.071, HR 1.49 [95% CI 0.97 2.31]). However, after adjustment for classic CV risk factors, a significantly increased risk of CV events among carriers of the minor allele A was found (p = 0.023, HR 1.72 [95% CI 1.076 2.74]). This latter model was adjusted for the presence or absence of at least one copy of the alleles belonging to the rheumatoid SE, therefore ascertaining the independency of both variables SE and the TNFA rs1800629 polymorphism. 3.2. Influence of TNFA rs1800629 polymorphism in the risk of CV events, according to the presence or absence of the SE In a further step we stratified our sample according to the presence of absence of the SE (Table 3). To do so, in Cox regression model described above we established a statistical interaction between the presence or the absence of the SE and the fact of carrying or not at least one copy of the minor allele A of the TNFA rs1800629 polymorphism. We found a significant interaction (p = 0.014), meaning that the effect of the TNFA rs18006229 polymorphism in the risk of CV events was different according to the presence or absence of SE. We observed that being a carrier of the minor allele A was associated with a higher risk of CV events but only in those RA patients with at least one copy of the SE (p = 0.003, HR 2.23 [95% CI 1.32 3.78]). This association between both variables was still maintained after adjustment for gender, age and classic CV risk factors (p = 0.024), and the significant association between carriers of the minor allele A and CV disease was only confirmed in those RA patients carrying the rheumatoid SE (p = 0.001, HR 2.43 Table 3 Association between TNFA rs1800629 polymorphism and the presence of cardiovascular events, according to a dominant pattern of effect, taking into account an interaction between this polymorphism and the presence or absence of shared epitope. p HR [95% CI] p a HR [95% CI] a GA + AA vs. GG SE+ 0.003 2.23 [1.32 3.78] 0.001 2.43 [1.41 4.19] SE 0.26 0.44 Interaction 0.014 0.024 SE, shared epitope; HR [95% CI], hazard ratio with 95% confidence interval. a Analyses adjusted for gender, age at rheumatoid arthritis diagnosis, presence or absence of rheumatoid factor, hypertension, diabetes, dyslipidemia, obesity and smoking habit. [95% CI 1.41 4.19]). In this regard, SE negative RA patients showed no association between this TNFA polymorphism and CV events (unadjusted p = 0.26, adjusted p = 0.44) (Table 3). In a recent study we described a significant association between the MHTFR rs1801131 polymorphism and the HLA-DRB1 0401*/0404*alleles with CV disease [5,8]. Taking into account these results, in the present study we assessed the combined effect of these two polymorphisms along with the TNFA rs1800629 polymorphism. Therefore, we analyzed the combined effect of these three genetic risk factors creating a variable ranging from 0 to 3 according to the number of genetic risk factors that were present. For this purpose we defined the following genetic risk factor: (1) being carrier of the minor allele C of the MHTFR rs1801131 polymorphism, (2) being carrier of the minor allele A of the TNFA rs1800629 variant and (3) the presence of at least one copy of the HLA-DRB1 0401*or 0404* alleles. We considered the number of genetic risk factors that were present regardless of the type of genetic risk factor that was present. Using this new variable we performed a Cox regression model that was adjusted for gender, age at RA disease diagnosis, presence or absence of rheumatoid factor, hypertension, diabetes, dyslipidemia, obesity and smoking habit. Following this procedure we observed that only when these three genetic risk factors together were present the association with CV disease was significant (p = 0.019, HR 3.07 95% CI [1.21 7.79]). 3.3. Influence of TNFA rs1800629 polymorphism in the presence of subclinical atherosclerosis Regarding the surrogate markers of subclinical atherosclerosis, we observed that patients who were homozygous for the minor allele A had higher values of carotid IMT and lower values of FMD% and NTG%. However, the low number of patients carrying this genotype (3 from the group in whom carotid ultrasonography was performed and 4 from those in whom a brachial ultrasonography was carried out) did not allow us to draw any strong conclusion (Table 4A). On the other hand, when we grouped the patients who carried of the minor allele A (GA + AA) and compared them with the remaining patients (those carrying the GG genotype), we did not observe significant differences regarding any surrogate marker of subclinical atherosclerosis. Also, in the ANCOVA model (Table 4B) and after adjustment for demographical and classic CV risk factors, we did not find significant differences regarding carotid IMT values, FMD% and NTG%. 3.4. HLA-DR3 and CV disease Due to the linkage disequilibrium between the TNFA rs1800629 polymorphism and HLA-DR3, we assessed the presence of HLA- DR3 in a subsample of both cohorts (n = 481). Fifty-seven patients (11.9%) carried at least a copy of HLA-DR3. We observed a significant association between the presence of HLA-DR3 and the presence of the minor allele A of TNFA rs1800629 polymorphism (p < 0.0001). Due to this linkage between HLA-DR3 and TNFA rs1800629 polymorphism, we assessed the effect of HLA-DR3 in
L. Rodríguez-Rodríguez et al. / Atherosclerosis xxx (2011) xxx xxx 5 Table 4 (A) Comparison of carotid artery intima-media thickness, flow-mediated endothelium-dependent (post-ischemia) vasodilatation (FMD) and endotheliumindependent (post-nitroglycerin) vasodilatation (NTG), according to TNFA rs1800629 polymorphism. (B) Comparison of carotid artery intima-media thickness, flow-mediated-endothelium dependent vasodilatation and endotheliumindependent vasodilatation, according a recessive pattern of effect of TNFA rs1800629 polymorphism in an ANCOVA model. IMT mm, median (IQR) (A) GG (n = 70) 0.74 (0.19) AG (n = 35) 0.71 (0.16) AA (n = 3) 0.86 (0.18) GA + AA vs. GG 0.72 (0.16) 0.67 FMD%, median (IQR) p NTG% median (IQR) p GG (n = 84) 6.12 (5.49) 17.29 (7.71) AG (n = 42) 5.25 (4.00) 17.70 (7.73) AA (n = 4) 3.03 (2.21) 10.88 (6.16) GA + AA vs. GG 5.05 (3.91) 0.25 17.10 (7.79) 0.89 IMT FMD% NTG% (B) p GA + AA vs. GG a 0.92 0.11 0.40 FMD, flow-mediated endothelium-dependent vasodilatation; NTG, endotheliumindependent (post nitroglycerin) vasodilatation; IMT, carotid artery intima-media thickness; SD, standard deviation. a Analyses adjusted for gender, age at the time of ultrasonography performance, follow-up time and presence or absence of SE, hypertension, diabetes, dyslipidemia, obesity and smoking habit. the risk of suffering CV events. However, no significant associations were observed (p = 0.74). 4. Discussion The present study showed that RA patients carrying the minor allele A of the TNFA rs1800629 (G > A) polymorphism are associated with a higher risk of CV events, after adjustment for demographic and classic CV risk factors. Taking into account that the presence the rheumatoid SE has been repeatedly associated with endothelial dysfunction, CV events and a poor outcome of RA [5,6,25,26], we aimed to analyze the effect of the TNFA rs1800629 (G > A) polymorphism stratifying our series of patients according to the presence or absence of the rheumatoid SE. For this purpose, we introduced an interaction between the TNFA polymorphism and the SE in the Cox regression model. Following this procedure we observed that the association between the TNFA variant and CV events was only restricted to those patients carrying the SE. The higher CV risk and accelerated atherogenesis observed in patients with RA cannot only be explained by the presence of traditional CV risk factors [1,4]. This fact led to the notion that RA or a high-grade systemic inflammatory status act as independent risk factors, conferring predisposition to the pathogenesis of the atherosclerotic disease or accelerating the disease process in affected individuals [27]. Therefore, the interaction between SE and TNFA may implicate that the alterations produced by the TNFA rs1800629 itself are not strong enough to yield an increase in the risk of CV events. Regardless of potential controversies, most data suggest a potential role of the TNFA rs1800629 polymorphism in the regulation of TNFA gene expression [12]. However, no association between this TNFA variant and CV disease was observed in subjects without RA [28 33]. Therefore, it is plausible to think that some additional factors, such as those induced by the presence of the rheumatoid SE in patients with RA, may be required to experience a clinically p evident CV effect mediated by the TNFA variant. Although our data may also suggest that patients with RA carrying the A allele of the TNFA may have more severe subclinical atherosclerosis manifested by increased carotid IMT and worse values of FMD% and NTG%, the low number of patients analyzed who were homozygous for the TNFA rs1800629 AA genotype did not allow us to raise any strong conclusion about this finding. Our results are in accordance with the previously described deleterious effects of TNF- over endothelial cells such as promotion of endothelial dysfunction through impairing nitric oxide bioavailability, cell injury [34], and apoptosis and suppression of the activities of endothelial progenitor cells that may sustain endothelial repair [35]. TNF- also promotes endothelial injury through recruitment of immune cells, such as neutrophils, which can mediate tissue destruction. On the other hand, anti-tnf therapy has been associated with an improvement of endothelial function in RA patients with severe disease refractory to conventional disease modifying anti-rheumatic drugs [36]. Also, registry databases have shown that anti-tnf therapy may reduce the CV risk in patients with RA, potentially through a reduction in the inflammatory load [37]. 5. Conclusions Our findings suggest that the TNFA rs1800629 (G > A) gene polymorphism is associated with predisposition to CV complications in patients with RA. This predisposition seems to be restricted to individuals carrying the rheumatoid SE. Taking together; these results reinforce the potential implication of a genetic component in the development of CV disease in patients with RA. Competing interest The authors declare that they have no competing interest. Author s contributions LRR carried out genotyping, participated in the design of the study, data analysis and helped to draft the manuscript. CGJ performed the ultrasonographic studies and participated in the design of the study, data analysis and helped to draft the manuscript RPM participated in genotyping and data analysis. TRV participated in the acquisition and interpretation of data. LR participated in the acquisition and interpretation of data. JAM-F participated in the acquisition and interpretation of data. BF has been involved in the acquisition and interpretation of data and in revising it critically for important intellectual content. JM has made substantial contributions to conception and design of the study, acquisition of data, coordination and helped to draft the manuscript and has given final approval of the version to be published. MAG-G has made substantial contributions to conception and design of the study, acquisition of data, coordination and helped to draft the manuscript and has given final approval of the version to be published. Acknowledgements This study was supported by two grants from Fondo de Investigaciones Sanitarias PI06-0024 and PS09/00748 (Spain). This work was partially supported by RETICS Program, RD08/0075 (RIER) from Instituto de Salud Carlos III (ISCIII). References [1] Gonzalez-Gay MA, Gonzalez-Juanatey C, Martin J. Rheumatoid arthritis: a disease associated with accelerated atherogenesis. Semin Arthritis Rheum 2005;35:8 17.
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